What is my CIS trying to tell me
 

New engine. DC 13 Cams. Timed to 1.59/1.6. I have a 78 running great and I have been swapping parts between the two engines to get the 79 running.

Swapped the distributors, spark plug wires, coils, CD box still runs rough.

Did a smoke test of the engine, no leaks!

Won't run with the vac hooked to the distributor.

Location of the Distributor TDC Rotor position is different between the two engines for both distributors. IE 78 is normal with both distributors. 79 is in an advanced position to run with both distributors. One tooth on the distributor.

Pressures are normal. IE about .5 bar cold building to 2.4 bar running warm. Fuel pump is 4.5 bar.

I hooked the fuel pressure meter in line with injector #1. Pressure built to just below 2 bar then rose to just below 3 bar and then just fell off back to just below two bar. Engine seemed to run the same.

Does the different grind on the cams affect the location of the distributor tdc?

Engine is timed to run 5 degrees before TDC, per the book.

I know mixtures are off some but they are close enough to run for the moment.

Lawd help me if the car was in a shop. I would have thousands in new parts with no resolution.!!

How does it run when it does ?

Vacuum to the distributor should be above the throttle plate and have no effect except in high RPMs
The cams are timed to the crank so it should have no effect on the timing.

Bruce

The engine runs but when you hook up the vac line to the distributor it runs rough and quits. It acts like there is an air leak, but a smoke test did not uncover it. I am slowly leaning the engine in the hopes of finding a balance where I can hook up the vac line. What do you mean that vac to the distributor should be above the throttle plate?

as long as the rotor points to #1 on the cap, it really does not matter how the dizzy goes in. but you may want to make it right.
make sure you plugged #1 wire to the same connection on both caps. verify firing order.

if the idle is low, and you connect the vacuum to the dizzy, it will cut the motor off. i think the timing is set at 4k RPM with the vacuum removed and plugged. once that is set connect vacuum and set idle then set mixture.

you may need to idle it up to connect the vac. leaning it will not help and not sure why you are doing that.

You may be one of the few people in the US who really understands the CIS. SmileWavy I am one of the vast unwashed who doesn't understand the thing. :confused:Thanks for the lead. I'll try again to set up the timing then tackle the mixture. I may (in the end) have fuel distributor problem. There must be a diaphram somewhere in the system that adjusts fuel pressure. I say that because on this car (the 79) when I hook the fuel press gage in line with an injector (I have done two) the indication is the reading rises from just below 2 bar and goes up slowly to just below 3 bar and then suddenly falls back to just below 2 bar. The time is as long as it take you to say two mississippi's. The 78 does not act that way. The indication is steady for the most part and when you actuate the accellerator it will dip and retrun to about 3 bar.

Since this is a rebuilt motor could it be generating too much vac over say an older engine??

Set the timing a 5 btdc at 4K. It was different. Also changed the rotor button. For some reason the new one had a smaller shoe than the old one. Ran smoother with that move. Then I got it running and idling at 1K with vac off and closed off. Then I put the vac on and it began to run very rough and backfired thru the muffler loud enough to wake the neighbors dog two houses away. Will now start, idle and run. Gonna replace the plugs today. Also pulled each plug wire, in turn, and all caused a small rough in the engine. Why does the vac to the distributor cause such a wild running engine?

If you go to the op of he page you will find a tech info tab, go there and scroll dwn you will seee what you need ..I hope

the timing is suppose to be about 24 BTDC or so. i dont have a spec book in front of me for that motor, but 5 BTDC is not right.
i dont know if the pressure to the injectors that you are seeing is that big a deal at the moment. if the CIS sat for a long period of time it could have some issue due to gas sitting in the FD head. get it running and run some techron thru it, give it several tanks. i would be more concerned that ech injector is providing the same fuel volume. i put each injector in a cup, turned the key on, lifted the plate in the air flow meter for about 30 seconds. then i weighed the fuel in each container, using a common container, to determine fuel volume. i had one that was putting out half of what all the others were, turned out i had a bad injector line.
make sure the plugs are good like you said. check the spec on the timing and set. you may have to adjust the idle to connect the vac, then go for the mixture.
since you have gages, go ahead and check your control presures.
when you connect the vac, not only will it bring the RPM down, it will make it run leaner thus the backfiring, although it usually backfires thru the air box. you do have a popoff valve?

Thanks. Timing for 78/79 is 5 BTDC. 81 is 25 BTDC.

You are correct. it is 24-31 BTDC at 6K with vac control detached. Per little white spec book.

One new observation. On the 78 the vac for the distributor is hooked to a port at the rear of the engine. On the 79 the vac is hooked to a port on the front of the engine at the throttle plate. I cannot tell from the vac diagrams in the maint manual which is correct. Anybody know?

Both cars have the air pump removed. Otherwise they are the same. I am going out today and buying a vac gage, Don't know why I haven't owned one to date.

I think your first step should be to verify the mixture. It is crucial. You may find this to be the problem.

Seems strange that hooking up the vac advance line at idle would have any impact on the running condition.

My 82 has the advance and retard vac lines. Pulling the advance at idle does nothing - pulling the retard at idle will increase the idle.

Your advance line isn't "sucking" is it? Meaning, if you put your finger on the end of it with the car running do you feel it sucking?

In fact it does suck. Clocks 15" at idle. (new vac gage today). The 78 registers "0" at idle and goes to 12" at 5Krpm.

Re set timing. Didn't take much. Was pretty close.

Tomorrow... new plugs. Try to find out if the vac to the distributor comes from the vac point at the rear of the engine (which I suspect is correct and the way the 78 is) and if it is I must lower the engine to get to the port. 1 hr job. I may be closer than I think. I am beginning to think I have been chasing goasts. :)

Incidently, I cannot tell from the vac diagrams which port is which.

The advance vacuum line shouldn't be sucking at idle as far as I know. Is it possible that you are attaching a retard vacuum line to your advance nipple?

I don't know when the advance and retard combo was added to the SC but you will find TONS of CIS pics by clicking on my signature link - pics for the 80 and 82 SC.

Surely someone can tell you where the advance line connects.

See the orange line in the pic below? This is where my advance line connects.


http://forums.pelicanparts.com/uploa...1238103076.jpg

Retard line connects at orange arrow (rear of car - fan side).

http://forums.pelicanparts.com/uploa...1238103701.jpg

the last thing you do is mixture. timing will effect the mixture, so get all that straight then you can do a final on the mix

MCA you may have hit the ball out of the park. It is beginning to make sense. My distributor only has one vac connection, not like the 81-on. How the lines got screwed up I don't know (if this is the solution).

Will do the mix last, thanks.

Yes, make sure your timing is correct first.

To me, those are the first two steps (timing / mixture) b/c it is ez. Then if it still runs poorly you investigate other areas.

Always good to check your CIS pressures, injectors and look for leaks. Sounds like these are all good at this point based on your testing. Therefore it makes sense to set the timing and adjust the mixture and not go poking around at other stuff. Just my 2 cents.

Today a friend came by with his hi falootin meter and set my mixture. Co 2,0/2.5, CO2 6.0 and 02 was 5% but HC was off the scale. Still runs rough.

To recap. Standard 3.0 O/H with new cylinders, pistons. Head work done. DC13 Cams installed.

Bottom line. His analysis, and he is one of the best in the area, is the injection system is ok. All system pressures are normal. The problem is the cams. The engine won't run with the vacuum hose hooked to the distributor. Backfires, cusses, runs rough, won't do anythng but idle. He suggested new injectors might help some since the old ones have 30-40K since a Marren injector tune and 150K total.

Vac hose to distributor is blocked.

I did not expect these problems with a DC13 grind on the cams. My mechanic friend is suggesting I go back to SC Cams and scrap the DC13s. Uggggg. More work.

If you read thru above you will see I have swapped out most stuff and now my engine is a combination 78/79 as far as parts go. The vac hose set up is the same between the two cars.

My advice to others. Don't screw with the SC unless you have a bottomless pit of money and expert help.

I'm gonna go drink another beer!:mad:

Don't be so quick to yank the cams. Let some others chime in regarding that specific grind.

Did you guys look at your ignition timing? Did you check your cam timing?

You car should run regardless of whether or not the advance vacuum line is hooked to the dizzy.

Other things to check would be the spray pattern of the injector which you can do on or off of the car - do a search on this. Could be bad injectors or a bad fuel distributor.

You must be frustrated but hang in there. Lots of other possibilities. How much more frustrated would you be if you pulled the cams and it still didn't run right?

2.4 bar warm? seems low. i thought spec was around 3.4. your car has the vacuum WUR, if this is not connected to the correct port or the vac part in the WUR is bad, this will give you the 1bar drop from 3.4 to 2.4 bar. the vac port on the the WUR is on the side or bottom. it may go to a small device called the thermo time valve TTV with an electrical conection then to the TB. if the TTV is bad, it can drop your CP to 2.4 bar.

Thanks. No warm pressure is 3.0 - 3,2 steady. System pressure is 5.0. Leak down is several hours. Cold is 2.0 plus some. Very good mechanic has passed on the WUR and besides it has been swapped between the other car at least twice. Pretty sure the WUR is not the problem. New injectors are on order but won't be here for a week or so. I wrote to Camgrinder today and hope he has some ideas. By the way, my mechanic has been fixing only Porsches since the early 356 days and has a shop specializing in only Porsches. He know his business and he warned me not to vary from Stock, advice I did not take, dumb me.

Car has SSI's.

Boy when it backfires with the vacuum attached it will wake up every dog in the neighborhood!

your first post said 2.4 bar warm.

funny, i just gave someone else the same advise about going back to stock. when things are working fine, then change to see what might work better.

you say you jusr got a vacuum pump? nice tool to have. put it on the dizzy and verify it is making the timing retard and how much. then check TB connection. retard should have vac at idle only, advance will have vac above idle.

i dont think it is the cam unless a mistake was made when they were timed and they are not timed correctly. someone put mine in 15deg's off. guys here are using 964 and DC20 cams without problems. recurve of the dizzy may help drivability but it sounds like you are having your problems at idle. no?

does it backfire at idle or when you give it gas?
when you connect the vac retard, you do realize that changes the mixture and it will lean it out.

do you have the vac port on the WUR and is it connected

Thanks a lot for the help with my 79. I am going to be away for a few days but when I get back I will start again at ground "0". Will get all new measurments and start the thread again. Camgrinder wrote back and said he doubted the cam because teh DC13 is a mild grind and offered to regrind it to SC and no charge. Nice offer. Since I have the 78 and it is running great, I'm going to put em back to back and keep going until I find something. Since the mixture is set, I'll leave that alone for a while. The WUR has a vac line and it is attached at both ends. Will install the new injectors when I get them. Thanks.

Incidently it backfires when you add gas and the vac line is attached.

check that vac line. if it idles fine, that line may not be connected to the proper port. that vac lline acts like an accelerator pump on a carb. it makes the CIS dump more fuel in for a split second to help with the added dose of air. helps to improve throttle response